Process simulation of oxy-fuel combustion for a 300 MW pulverized coal-fired power plant using Aspen Plus

Abstract

This work focuses on the amounts and components of flue gas for oxy-fuel combustion in a coal-fired power plant (CFPP). The combustion process of pulverized coal in a 300MW power plant is studied using Aspen Plus software. The amount of each component in flue gas in coal-fired processes with air or O2/CO2 as oxidizer is obtained. The differences between the two processes are identified, and the influences of temperature, excess oxygen ratio and molar fraction of O2/CO2 on the proportions of different components in flue gas are examined by sensitivity analysis. The process simulation results show that replacing atmospheric air by a 21%O2/79%CO2 mixture leads the decrease of the flame temperature from 1789°C to 1395°C. The equilibrium amount of NOx declines obviously but the SOx are still at the same level. The mass fraction of CO2 in flue gas increased from 21.3% to 81.5%. The amount of NOx is affected sensitively by the change of temperature and the excess oxygen ratio, but the change of O2/CO2 molar fraction has a little influence to the generation of NOx. With the increasing of O2 concentration, the flame temperature and NOx emission enhance rapidly. When the molar fraction of O2 increases to 30%, the flame temperature is similar and the mass fraction of NOx is about 1/8 of that air atmosphere.